Biaxially-oriented nylon film (hereinafter also referred to as ONy film), which is excellent in strength, impact resistance and anti-pinhole property, is frequently used for packaging a product such as a heavy product or liquid product on which a great load is applied.
There has been conventionally known a technique to use nylon for a packing material used in such a forming as a deep-drawing, a stretch forming or the like (see e.g. Patent Document 1, Patent Document 2).
Specifically, Patent Document 1 discloses resin sheet for cold forming that includes: a base material layer that contains a polystyrene-based resin; and a functional layer that is single-layered or two-layered on both surfaces or one surface of the base material layer. In addition, according to Patent Document 1, as the functional layer, an abrasion resistance layer that contains a nylon resin is provided on an exterior layer of the resin sheet for cold forming.
According to such resin sheet for cold forming, a cool-formed article that is excellent in impact resistance and shape-retaining property can be obtained. By providing the abrasion resistance layer containing the nylon resin on the exterior layer of the sheet, the exterior layer of the sheet can be prevented from being damaged during cool-forming.
As described in Patent Document 1, as compared with hot-forming, cool-forming is excellent in that a size of an apparatus can be reduced with a heater being omitted and that a continuous forming at high speed can be realized.
On the other hand, Patent Document 2 discloses composite sheet for deep-drawing that is formed by laminating plural pieces of sheet that includes a seal layer, a middle layer and an outer layer. In the sheet, the seal layer includes a polypropylene-based resin layer, the middle layer includes an oxygen-barrier resin layer, a nylon-based resin layer and a polyethylene-based resin layer, and the outer layer is made from a hygroscopic material.
According to such composite sheet for deep-drawing, the composite sheet can be given a mechanical strength by providing the nylon-based resin layer in the middle layer. With this arrangement, an occurrence of a pinhole during deep-drawing at approximately 150 degrees C. can be prevented.    [Patent Document 1] JP-A-2004-74795    [Patent Document 2] JP-A-2004-98600